Oct 31, 2011

How to make arrow objects for Google Earth

In the previous post, we has use GeoDestination function to make circle objects, and we can use the same function to generate arrow objects, too.

The data we have is the position and displacements in north and east direction, {lat, lon, ndis, edis}. ndis, edis is in millimeter in this case.

First, let calculator the length of the arrow, the scale here is 1 mm displacement = 1000 meters

length = Sqrt[ndis^2 + edis^2]*1000

Then the angle. GeoDestionation requires GeoDirection, it starts from the north.

angle = ArcTan[edis, ndis] /Degree
geoangle = 90 - angle

For the end point:

end = First@GeoDestination[{lat, lon}, {length, geoangle}]

The trick to generate the arrow is that to form another smaller circle around the end point, pick up two points from the arrow heads. 

arr1 = First@GeoDestination[end, {dist*.25, geoangle + 180 - 30}]
arr2 = First@GeoDestination[end, {dist*.25, geoangle - 180 + 30}]

Then we can have two lines which draw in this order, {org –> end}, {arr1->end->arr2}. When comes to export kml, we need to use <MultiGeometry> object in KML, it seems not supported by Export function in Mathematica yet, so you can just export the following string directly:

-117.093195026,34.116408002,0 -117.020521006,34.0741018797,0
-117.042636322,34.0757361767,0 -117.020521006,34.0741018797,0 -117.029869517, 34.0907835742, 0

Here is the screenshot of the final product in Google Earth:



Szabolcs said...


I did not find any contact details, so I'm writing in a comment. I wanted to let you know about a proposal to create a questions/answers site about Mathematica in a similar format to StackOverflow (http://stackoverflow.com/questions/tagged/mathematica) If you are interested, you can help launch the new site by committing to it ("commit" button), and perhaps by mentioning it in the blog as well. Please see http://area51.stackexchange.com/proposals/37304 If you are not interested, please remove this comment.

Pocha huntas said...

Your content shows the power, I’m about to add this to my bookmarks.

general recreation inc

SoftwareCorner said...

"I think this article contains huge valuable information about mortgage. This article can help by preventing risk.
Truly its a nice job. Thank you for sharing with us. "

Jullia Grace said...

It’s a classic great for me to go to this blog site, it offers helpful suggestions life insurance rates

Roney Wilson said...

Hmm!! This blog is really cool, I’m so lucky that I have reached here and got this awesome information.car insurance full coverage